fix!: Remove non-functional borderData from PieChartData

[mahmoodhamdi]

Problem

PieChartData inherits borderData from BaseChartData, but PieChartPainter never uses it to draw any borders. When users set borderData: FlBorderData(show: true) on a PieChartData, nothing happens — the parameter is silently ignored.

This was reported in #1182 and confirmed by the maintainer.

Solution

Removed the borderData parameter from PieChartData:

• Removed from constructor, copyWith, lerp, and props
• PieChartData now always passes FlBorderData(show: false) to BaseChartData
• Updated documentation, example app, and tests

Users should use PieChartSectionData.borderSide for section borders.

Breaking Change

Code that passes borderData to PieChartData(...) will get a compile error. The fix is to simply remove the borderData parameter — it was never functional.

Migration:

// Before
PieChartData(
  borderData: FlBorderData(show: false), // remove this
  sections: [...],
);

// After
PieChartData(
  sections: [...],
);

Testing

• All 573 existing tests pass
• flutter analyze — zero warnings
• make checkstyle — passes
• Removed tests that validated borderData equality on PieChartData

Checklist

• flutter analyze passes with zero warnings
• flutter test passes (573 tests)
• dart format . applied
• CHANGELOG.md updated

Closes #1182

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.92%. Comparing base (d3a8ac2) to head (e0e5a9a).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2066   +/-   ##
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  Coverage   92.92%   92.92%           
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  Files          50       50           
  Lines        3873     3873           
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  Hits         3599     3599           
  Misses        274      274           

Flag	Coverage Δ
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[imaNNeo]

Comment from here:

Removing it will cause a breaking change for users who are using this property (even though it doesn't do anything).

On the other hand, I think there might be a use case where users want to have a rectangular border around the chart, and they can use this property. This way, we keep it consistent with the other chart types (as we have it intentionally in our BaseChartData).

I'm sorry, but I was wrong in my previous comment. Now I'm seeing it from a different perspective. Let's keep it and make it functional.